Design and Simulation for a High-efficiency Class-B Power Amplifier

MATEC Web of Conferences, Jan 2017

A class-B power amplifier with high output power and high power added efficiency (PAE) is designed in this paper. Based on the ADS tools of load-pull and source-pull, the optimal load impedance and source impedance can be obtained, respectively. Then, the matching circuit have been achieved by combining the impedance matching technique. Simulation results show that the class-B power amplifier has the PAE of 69.386% and output power of 45.32dBm with the working frequency of 960MHz. Therefore, It is a high-efficiency class-B power amplifier.

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Design and Simulation for a High-efficiency Class-B Power Amplifier

MATEC Web of Conferences Design and S imulation for a High-efficiency Class-B P ow er Amplifier Wei Jiang 1 Qian Lin 1 Haifeng Wu 0 0 Chengdu Ganide Technology Co Ltd , Chengdu, 610000 , China 1 College of Physics and Electronic Information Engineer, Qinghai University for Nationalities , Xining, 810007 , China A class-B power amplifier with high output power and high power added efficiency (PAE) is designed in this paper. Based on the ADS tools of load-pull and source-pull, the optimal load impedance and source impedance can be obtained, respectively. Then, the matching circuit have been achieved by combining the impedance matching technique. Simulation results show that the class-B power amplifier has the PAE of 69.386% and output power of 45.32dBm with the working frequency of 960MHz. Therefore, It is a high-efficiency class-B power amplifier. 1 Introduction Nowadays, all the major wireless standards-GSM, DMA,WCDMA, 802.11 a/b/g/n, WiBro and WiMax- are being integrated into a single package and widely adopted in the wireless communication system. A radio that integrates all of this functionality onto a single chip is urgently needed. One of the major impediments to addressing all these needs is the RF front end, specifically, the power amplif ier (PA). That is to say, the compact and fully integrated radio frequency (RF) and microwave front-end products are the indeed demand for the rapid development of the wireless communication system. As a result, achieving simultaneously high efficiency and high linearity remains one of the major challenges in microwave PAs. To our knowledge, PA is the core component of the wireless transmitter, its main function is to increase the RF power enough, which is effectively transmitted to a receiver through air medium. As the key equipment for the modern wireless communication, PAs have been widely applied in satellite communication, radar, wireless communications, navigation, electronic counter measures etc [1]. As mentioned above, in order to obtain the largest output power within a certain frequency range, the power transistor often works near the saturated state. At this point, its S parameters often change with the variation of the input signal, and the power gain will become smaller. In other words, the output/input of conjugate match gradually will become mismatching due to the small signal input. Then, it can not be able to obtain the maximum output power [ 2 ]. Therefore, the key point for PA design mainly lies in the design of matching network. The technology of load-pull is the major method to find out the optimum load impedance corresponding to * the largest output power. Meanwhile, the optimal source impedance can be obtained by the technology of sourcepull. Finally, the output and the input matching circuit can be achieved, respectively. Furthermore, comparing with the other PAs, Class-B PA has better linearity and higher power efficiency, for which its PAE can reach about 78.5% theoretically [3]. The DC working point for the power transistor of the class-B PA is often biased at the breakpoint [4], then the DC output current is zero. When the AC signal is used as the input, the power transistor switches on in a half cycle and switches off in the negative half cycle of AC signal. This operation mode of half cycle for class-B PA has remarkable advantages over Class-A PA. Moreover, the microwave field effect transistor (FET) of class-B PA can cause the increase of power efficiency and substantial reduction of both DC power and heat dissipation. Therefore, how to keep high efficiency and high power is the major challenge for the class-B PA. The design strategies and implementation of a high efficiency class–B power amplifier based on the Freescale FET of MRFE6S9046 are presented in this paper. The simulation results show that the power additional efficiency (PAE) is 69.39% with output power of 45.32dBm when the input power is 26.5dBm in the working frequency of 960 MHZ. Thus, the demands of high performance and high efficiency can be achieved by comparing with the class-B PAs reported in exiting literatures. This paper is organized as follows. The design of a high efficiency class-B PA is introduced in detail in Section II. Then its matching circuits of the source input impedances and the output impedances have been presented in Section III. In Section IV, the measured results of this PA are discussed as well as the conclusions. 2 Design of the class-B power amplifier The circuit schematic of the class-B PA based on the FET of Freescale MRFE6S9046 is given in Fig.1. It can be observed that it is consisted with the signal source, input matching circuit, power transistor, DC bias circuit, the output matching circuit and the load. Furthermore, based on the datasheet of this transistor, it can be known that when the PA works in the typical GSM mode. In this way, the DC bias circuit is used to set the appropriate working point for the power transistor. (...truncated)


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Wei Jiang, Qian Lin, Haifeng Wu. Design and Simulation for a High-efficiency Class-B Power Amplifier, MATEC Web of Conferences, 2017, 139, DOI: 10.1051/matecconf/201713900056